Evaluate Conservation Solutions Practice Test

A river has fewer native trout after summers with low water levels and warmer temperatures. The county will evaluate solutions using multiple criteria: scientific criteria (water temperature, dissolved oxygen, trout survival, other species) and economic/social constraints (water for farms, project cost).

Evidence:

• When water temperature rises above 20°C, trout survival drops by 30%.
• Solution 1: Release cold water from an upstream reservoir in July–August. Predicted: lowers river temperature by 2°C and raises oxygen by 0.5 mg/L; but reduces water available for irrigation by 10% and costs $15,000 in operations.
• Solution 2: Plant trees along 8 km of riverbank for shade. Predicted: lowers temperature by 1°C after 5 years; costs $120,000; requires temporary access restrictions on two private properties.
• Solution 3: Stock hatchery trout. Predicted: increases trout numbers quickly, but evidence shows stocked trout have 20% lower survival the next summer and may compete with wild trout for food.

Which prediction about solution effectiveness under the constraints is supported by the evidence?

A lake has an invasive plant that blocks sunlight and lowers oxygen for fish. The community will evaluate solutions using multiple criteria: scientific effects (oxygen levels, native plant recovery, fish survival) and economic/social constraints (budget $80,000, boating access).

Evidence:

• Current dissolved oxygen averages 4 mg/L in summer; many fish species need at least 5 mg/L.
• Solution 1: Mechanical harvesting costs $70,000 per summer, removes 60% of invasive plant biomass, but can also remove 10% of native plants; boating lanes stay open.
• Solution 2: Herbicide treatment costs $40,000, reduces invasive biomass by 80%, but causes a short-term oxygen drop of 1 mg/L for about 2 weeks; the lake is closed to swimming for 1 month.
• Solution 3: Introduce a plant-eating fish costs $20,000, but evidence from nearby lakes shows it also eats native plants and reduced native plant cover by 30%.

Which statement correctly weighs the criteria and evidence when evaluating the solutions?